1. Field of the Invention
The invention relates to a method and apparatus for laying and maintaining railways and, more particularly, relates to a method and apparatus for applying spring clips in anchor sockets.
2. Description of the Related Art
The use of spring clips to fasten rails to concrete or wooden ties is becoming increasingly popular. The clip most commonly employed is manufactured by Pandrol Incorporated of Bridgeport, N.J. and is formed from a steel bar bent generally into the form of an "e". Such a clip, commonly known in the art as a "Pandrol e" clip, is used to fasten a rail to an anchor socket imbedded in a concrete or wooden tie by first loosely setting a center leg of the clip in the socket such that a toe of the clip loops back onto the base of the rail, and by then applying the clip by driving the clip further into the socket such that the clip applies substantial spring forces to the base of the rail.
The steps of setting and applying rail clips typically are performed independently of one another and have traditionally been performed manually with a first work gang manually setting the clips in the sockets and a second work gang driving the clips further into the sockets with sledge hammers. More recently, machines have been constructed which automatically apply clips after they have been manually set in the sockets. One such machine is disclosed in U.S. Pat. No. 4,320,707 to McIlrath (the McIlrath patent). The McIlrath patent discloses a clip applicator having arms which are mounted on a workhead and which can be hydraulically actuated to drive pincers into contact with a previously set clip to forcefully drive the clip into the socket, thereby applying the clip. While the clip applying machine disclosed by the McIlrath patent operates well, it still requires that clips be set in the sockets prior to application. This clip setting has heretofore been performed manually and thus is labor intensive.
Another machine, disclosed in U.S. Pat. No. 5,191,838 to Hansen (the Hansen patent), is designed to set and apply clips using a single machine. The machine disclosed by the Hansen patent includes a magazine, a clip shuttle which transfers clips from the magazine into alignment with anchor sockets, and a drive block which drives clips from the clip shuttles into the anchor sockets with sufficient force to apply the clips.
The machine disclosed by Hansen, though capable of applying clips which have not been previously set, exhibits several drawbacks and disadvantages. For instance, because the clip shuttle and drive block and associated components must be operated independently of one another yet must be capable of cooperating with one another at critical times, the machine disclosed by the Hansen patent is relatively large and complex. It also may be cost prohibitive to some customers, particularly those who already own a clip applicator and merely require a less labor intensive technique for setting clips.
Alignment of the machine disclosed in Hansen both longitudinally and transversely with respect to the rail and socket is relatively difficult and requires the operation of drive cylinders operable independently of rail clamps, stops, and other portions of the workhead.